Field of Invention
The present invention relates generally to the field of hydraulic circuits utilized in automatic transmission systems and, more particularly, to a replacement valve mechanism for an Actuator Feed Limit valve (hereinafter xe2x80x9cAFL valvexe2x80x9d) that regulates pressure within the Actuator Feed Limit circuit (hereinafter xe2x80x9cAFL circuitxe2x80x9d) of the valve body of the transmission.
Automatic transmission systems of the prior art have a hydraulic circuit subsystem which includes at least a hydraulic pump, a valve body having fluid conducting passages or circuits, input and exhaust ports formed within the fluid circuits, and a plurality of so-called spool valves comprised of modified pistons which alternately open and close the ports to regulate the flow and pressure of automatic transmission fluid (hereinafter xe2x80x9cATFxe2x80x9d) within the fluid circuits to actuate different components of the transmission.
It will be understood that in describing hydraulic circuits, ATF usually changes names when it passes through an orifice or control valve in a specific circuit. U.S. Pat. No. 5,700,226 entitled Hydraulic Lubrication Control System for an Automatic Transmission System is one example of a prior art reference relating to automatic transmission systems, which further explains the functions of such control valves and fluid circuits.
The AFL valve limits hydraulic pressure as ATF passes through the valve and enters the AFL circuit. Spring force acting on the AFL valve limits fluid pressure to a predetermined maximum amount. When line pressure is above this value, Actuator Feed Limit fluid (hereinafter xe2x80x9cAFL fluidxe2x80x9d) pressure moves the AFL valve against spring force to block line pressure and opens the actuator feed to exhaust thereby providing the limiting action.
Leakage can eventually develop within the AFL circuit due to wear between the valve piston and mating bore resulting in low boost pressure, improper gear shifting and clutch/band failure. The same AFL fluid loss results in lower line pressure, which is the main fluid pressure in the hydraulic system.
Thus, the present replacement AFL valve mechanism has been developed to provide a solution to these problems and to resolve other shortcomings of the prior art.
Accordingly, the present invention is a replacement valve mechanism for the original equipment manufacture (hereinafter xe2x80x9cOEMxe2x80x9d) AFL valve, which is standard equipment on the 4L60E and 4L80E transmissions made available on many vehicles produced by General Motors prior to 2001 and which will be referred to throughout this specification. The function of the AFL valve is to prevent the fluid pressure generated by the AFL circuit from becoming too high, which can result in flooding of the control solenoids and the valve orifices being unable handle the excess pressure.
The OEM design of the prior art AFL valve in the 4L60E and 4L80E transmissions has a large reaction area and is highly affected by side loading (i.e. vertical movement), which can adversely affect the response and accuracy of the valve and tends to wear the mating valve bores within the valve body prematurely.
The present invention provides a replacement valve mechanism comprising an AFL valve including a hard anodized valve piston that resides in a close tolerance, full contact sleeve component that provides inlet and exhaust ports about the entire circumference of the valve. This provides at least 50% more surface contact area than the OEM design and effectively eliminates side-loading of the AFL valve, which enhances AFL circuit control, reduces oscillation, and substantially reduces bore wear. By substitution of alternate compression springs having different spring rates and dimensional characteristics in a kit format, the present replacement AFL valve mechanism will fit either the General Motors 4L60E or 4L80E early and late design transmissions.
Thus, it is an object of the present invention to provide a replacement AFL valve mechanism including a full contact sleeve having inlet and exhaust ports disposed about its circumference, which substantially reduces side loading, bore wear and AFL fluid circuit leakage.
Another object of the present invention is to provide a replacement AFL valve with improved response and accuracy, which reduces torque signal oscillation and AFL fluid oscillation thereby enhancing AFL circuit control.
Another object of the present invention is to provide a replacement AFL valve which will eliminate improper gear starts, soft/delayed shifts, and low line pressure.
Another object of the present invention is to provide a replacement AFL valve in an aftermarket kit format including a reaming tool, which will fit both General Motors 4L60E and 4L80E early and late design transmissions by substitution of alternate compression springs having different spring rate and dimensional characteristics.
Other features and technical advantages of the present invention will become apparent from a study of the following description and the accompanying drawings.